Field of the Invention
The present invention relates to optical storage and more particularly to quantum dot constructed memory storage.
Description of the Related Art
Optical storage refers to an electronic storage medium which utilizes low-power laser energy to record and retrieve digital information from an underlying medium. In optical-storage technology, a laser beam encodes digital data onto an optical disc in the form of small pits arranged in concentric tracks on the surface of the disk. A low-power laser scanner reads the pits, with variations in the intensity of reflected light from the pits being converted into electric signals. Optical discs may permanently store information and, in that instance, are read-only. Optical discs may also be fully re-writable. Thus, optical discs may be viewed as an alternative form of fixed storage—an equivalent to a hard disk drive.
Optical storage is not limited to fixed storage, though. Modern advancements in quantum dot technology now enable the construction and use of high speed optical memories. A quantum dot is a small composition of matter, a crystal with a diameter on the order of nanometers, that is concentrated into a single point and thus is zero-dimensional. As a result, the particles inside the quantum dot that carry electricity—namely electrons and holes—become constrained within the quantum dot and demonstrate well-defined energy levels according to quantum theory. Generally, quantum dots are formed on a semiconductor substrate, and although quantum dots physically are crystals, quantum dots behave more like individual atoms and thus are often nicknamed “artificial atoms”.
Quantum dots are precise crystals, and thus are fabricated in the same way as any other precise semiconductors crystal. Typical methods include molecular beam epitaxy, ion implantation and X-ray lithography. In molecular beam epitaxy, beams of atoms are fired at a “base” or substrate so that a single crystal slowly builds. In ion implantation, ions are accelerated electrically and fired at a substrate. In X-ray lithography, an atomic-scale engraving process engraves the relevant crystalline features in the substrate utilizing X rays.
Optical computers use quantum dots in much the same way that electronic computers use transistors as the basic components in memory. In quantum memory, bits are stored not by transistors but by individual atoms, ions, electrons, or photons entangled and acting as quantum bits. More specifically, an optical memory controller writes data to an array of quantum dots by creating light and dark portions of the crystalline structure in which the quantum dots are formed. During a refresh phase, the controller maintains dark areas in the structure while re-illuminating light areas of the structure as laser light exists through the structure. Finally, during a read phase, the controller reads out from the crystalline structure dark and light areas and interprets the light and dark areas as binary digits. As will be recognized then, the atomic scale size of quantum dots permits the formation of highly dense high speed optical storage in which substantial volumes of data may be stored.